APC is gone, drop in replacements here

APC is gone, no longer maintained, now there are alternatives.

For opcode cache, PHP 5.5 (5.6 shipps with jessie) the opcode cacher ( OPcache ) module is installed and enabled by default, as for key cache (Persistent across pages), we have an alternative called APCu (Just the user key value cache), once installed, the apc_ functions return to PHP so it is a drop in replacement, no no program modifications needed.

To install APCu, you run the following

1- Install the tools
apt-get install apache2-threaded-dev php5-dev php-pear make
2- Before you get APCu-4.0.7, you should check what the latest version is !
pecl install channel://pecl.php.net/APCu-4.0.7

Now you are done, all you need to do is add
extension=apcu.so
to the php config file, in my case, what i do on debian jessie is add it in a file here
/etc/php5/apache2/conf.d/apcu.ini

There you have it, you are back on track.

Over provisioning SSD in linux

Over provisioning a Samsung 1TB 850 EVO

Mind you, Don’t follow this tutorial step by step unless you have a 1TB Samsung 850 EVO, if you have a smaller disk, you need to adapt the numbers to your SSD 😉

Over provisioning a flash disk is simply some un-partitioned space a the end of the disk, but you need to tell the SSD’s controller about that free space that it can use to do it’s housekeeping, You also need to find out if the Tejun Heo’s on-demand HPA unlocking patch applies to your distro, if it does, you need to get kernel patching first.

First of all, the controller will usually use the cache RAM to so the over provisioning, or at least this is what i understood from some text on the Samsung website, you can make things faster by allowing it to use FLASH space while it deletes a 1.5MB flash area to put the data in.

1- How big should the over provisioning area be ?

Samsung recommends 10% of the disk’s space. Somewhere hidden in a PDF on their websites, they explain that OP space should be anywhere between 7% and 50% ! we will use 10 as our writing patterns are not that harsh. but mind you, a database that alters a few rows every second can probably make the most use of such OP space.

2- Won’t that 10% wear out before the rest ?

No, there is a mapping function inside the controller where that space is in fact wherever the controller thinks is appropriate, the wear leveling algorithm kicks in at a stage after the logical stage of partitions etc… it is blind to the file system or the over provisioning area, it will simply remap any address you give it to a random address that is not already mapped, at flash erase, those mappings are deleted, and other areas of the disk will be assigned to that area, i have no idea whether it uses a random algorithm, or simply has a record of flash chip usage (At the size of the sample, that won’t make any difference.)

3- Are you sure we are informing the controller and not just telling Linux what the last address is ?

Sure I’m sure, ask the controller DIRECTLY yourself with the command

smartctl -i /dev/sdb

Before the operation we are doing in this article, it will say 1000204886016, and after it will say

User Capacity:    900,184,411,136 bytes [900 GB]

Meaning that now, the disk’s S.M.A.R.T. attribute tells us that this much is available for the user after the over provisioning operation

So, how do we over provision in linux

See the last secrot of your ssd,

hdparm -N /dev/sdb

In my case, my samsung 850 EVO has the following, notice that the number is repeated twice. x out of x is the same, and HPA is disabled..

max sectors = 1953525168/1953525168, HPA is disabled

Now, 1953525168 * 512 = 1,000,204,886,016 (1 TB !)

Now, we want to set a maximum address, anything after this address is a PROTECTED AREA, that the controller knows about, I will multiply the number above with 0.9 to get the maximum address, take the integer part alone

hdparm -Np1758172678 --yes-i-know-what-i-am-doing /dev/sdb (As hdparm -Np1758172678 /dev/sdb will ask you if you know what you are doing)

 setting max visible sectors to 1758172678 (permanent)
 max sectors   = 1758172678/1953525168, HPA is enabled

Now again, hdparm -N /dev/sdb

max sectors = 1758172678/1953525168, HPA is enabled

Now, to make sure we are not suffering that dreaded bug, let’s reboot the system and check again after that, I am using debian Jessie, so it is unlikely that i am affected

Yup, hdparm -N /dev/sdb still gives us a smaller maximum address than the actual physical

Now, we seem to be ready to talk fdisk business.

fdisk /dev/sdb

Now, if you O (Clean), then P, you should get a line such as

Disk /dev/sdb: 838.4 GiB, 900184411136 bytes, 1758172678 sectors

This means that FDISK understands.and asking it to create (the n command) will yeild this

/dev/sdb1 2048 1758172677 1758170630 838.4G 83 Linux

Arent we happy people.

Now, lets mount with trim support, and enjoy all the beutiful abilities an SSD will bless us with.

tune2fs -o journal_data_writeback /dev/sdb1
tune2fs -O ^has_journal /dev/sdb1

Alliance ProMotion 6410

One little problem about modern VGA cards is HEAT, they consume over 30W on IDLE, those 30 watts are going into the case, so i looked into my old computers, and found a computer that dates back to 1995-1996, I pulled out the VGA card from it, and installed it on a modern I3 computer for testing pending the installation on an I7 with 64GB of ram and what have you.

On ebay, you can find such PCI cards for around $10, Cirrus Logic, SIS, ATI, OR S3, they should all work, if the promotion card works, those should work too.

Now i ran the Debian Jessie installer, the installation went fine, when rebooting, the system boots with the PCI card, but then switches to the embedded graphics system (Comes with the I3 CPU), the BIOS does not allow me to disable that, so, rather than looking for a solution, I will test the adapter on an I7 (Does not come with built in VGA).

I have a good feeling that it will work right away, here is some information about my 20 year old graphics card (Will post some photos too when i plug it out)

    Made by: Alliance
    Codename: ProMotion 6410
    Bus: PCI
    Memory Size: 1MB
    Max Memory Size: 4MB
    Memory Type: FPM
    Year: 1995
    Card Type: VGA
    Made in: USA
    Owned by: Palcal
    Outputs: 15 pin D-sub
    Power consumption (W): 1.5
    Video Acceleration: MPEG-1 (VCD)
    Core: 64bit
    Memory Bandwidth (MB/s): 213
    Sold by: miro
    Press info: Freelibrary

You can find